1. Field of the Invention
The present invention relates to the use of a hydroquinone compound with hydrazine (1:1 molar ratio) as an oxygen-scavenger and corrosion-inhibitor in fluidic systems.
2. Description of the Prior Art
Dissolved oxygen in fluids such as water may promote extensive pitting and other forms of corrosion to metal surfaces coming in contact with these fluids. For example, this corrosion may cause serious problems such as metal failure to boiler systems, hot water heating systems, and the like.
Accordingly, removal of oxygen from fluidic streams and systems is highly desirable in many instances. Such deoxygenation can be carried out by either mechanical or chemical means or with both. In those situations where chemical deoxygenation is desired, various chemicals including sodium sulfite, hydrazine, and hydroquinone have been employed as chemical oxygen-scavengers. See U.S. Pat. Nos. 3,551,349 (Kallfass); 3,843,547 (Kaufman et al); 3,983,048 (Schiessl); 4,012,195 (Noack); 4,022,711 (Noack); 4,022,712 (Noack); 4,026,664 (Noack); 4,079,018 (Noack); 4,096,090 (Noack); and 4,269,717 (Slovinsky) as teaching of the use of hydrazine or similar compounds as oxygen-scavengers and corrosion-inhibitors. See U.S. Pat. Nos. 4,278,635 (Kerst); 4,279,767 (Muccitelli); and 4,282,111 (Ciuba) as teaching of the use of hydroquinone and the like as an oxygen-scavenger. All of these cited U.S. patents are incorporated herein by reference in their entireties.
Hydrazine, with or without one or more catalysts, has long been used as an oxygen-scavenger to remove dissolved oxygen in liquid systems such as boilers and hot water heating systems. The products of the hydrazine-oxygen reaction are nitrogen and water. Thus, no solids are added to the liquid system. Besides the oxygen-scavenging effect, hydrazine has a number of desirable effects in such systems. For example, it promotes passivation of steel surfaces, primarily by formation of magnetite surface coatings. In its reaction with red iron oxide to form magnetite, the by-products are also nitrogen and water, two innocuous substances. Decomposition of hydrazine in such systems also produces ammonia, whose alkaline effect on steam and condensate systems may be beneficial in some instances.
However, hydrazine is a liquid with appreciable vapor pressure even at ambient temperatures and in aqueous solutions. For example, when an aqeuous solution containing about 35% by weight N.sub.2 H.sub.4 is allowed to equilibrate with its vapor in a closed space, there may be up to 500 parts by volume per million parts of air in the vapor space over the solution. Moreover, hydrazine is toxic to humans by skin contact and by inhalation. The inhalation toxicity may be aggravated by the vapor pressure of hydrazine, depending upon the use. Accordingly, precautions should be taken in the workpiece to obviate the possibilities of skin contact and inhalation of hydrazine. Furthermore, the hydrazine-oxygen reaction is very slow at low operating temperatures such as room temperature. In those cases, one or more catalysts must be added to the system with the hydrazine.
Hydroquinone itself is also a known oxygen-scavenger. However, it also has certain disadvantages. It has the obvious disadvantage of adding dissolved solids to the system being treated. It also has the further disadvantage of being costly in terms of reducing effectiveness (i.e., much greater amounts of it are needed for an equivalent oxygen-scavenging function as compared to hydrazine). Furthermore, there is no known practical way to measure its residual concentration in commercial fluidic systems being treated.
As mentioned above, the rate of reaction between hydrazine and oxygen at room temperature is relatively low. Thus, the corrosion-inhibiting effect of hydrazine on metal surfaces may be unsatisfactory. For this reason, it has been proposed in the past to add catalysts or activators with the hydrazine to greatly accelerate the rate of reaction between hydrazine and oxygen, especially at room temperature. Among the known catalysts are the following:
______________________________________ Catalyst Reference ______________________________________ 1. water-soluble o- and U.S. Pat. No. p-quinone compounds 3,551,349 (Kallfass) 2. mixture of an aryl amine U.S. Pat. No. compound and a quinone 3,843,547 (Kaufman, compound Schiessl, and Csejka) 3. an aryl amine compound U.S. Pat. No. 3,983,048 (Schiessl, Kaufman, and Csejka) 4. an organometallic complex U.S. Pat. No. which is the reaction 4,012,195 (Noack) product of a cobaltous, manganous, or cupric inorganic salt and one or more ortho aromatic ligands containing at least one amino and one hydroxy group 5. a mixture of a quinone U.S. Pat. Nos. compound and an organo- 4,026,664 and metallic complex which is 4,096,090 (Noack) the reaction product of a cobaltous, manganous, or cupric inorganic salt and one or more ortho aromatic ligands contain- ing at least one amino and one hydroxy group 6. an organometallic complex U.S. Pat. No. which is the reaction 4,022,712 (Noack) product of a cobaltous, manganous, or cupric inorganic salt and one or more ligands comprising amino derivatives of carboxylic acids or salts 7. a mixture of a quinone U.S. Pat. Nos. compound and an organo- 4,022,711 and metallic complex which 4,079,018 (Noack) is the reaction product of a cobaltous, manganous, or cupric inorganic salt and one or more ligands comprising amino derivatives of car- boxylic acids or salts ______________________________________
In spite of all these teachings it is still desirable to find a new oxygen scavenger which retains all of the benefits of hydrazine and hydroquinone, yet removes one or more of above-noted undesirable effects of these compounds without the use of catalysts.
The present invention achieves such a solution to this need by providing (1) a non-volatile derivative of hydrazine which can be handled in the workpiece without the danger of inhalation but which, in the boiler or hot water system or the like, functions better than free hydrazine and (2) incorporates the additional benefits of hydroquinone without introducing excessive amounts of dissolved solids which may result from normal use of this reagent.
Furthermore, while this work with hydrazine and hydroquinone was going on, no one until the present invention recognized that the reaction product of hydrazine and hydroquinone could be employed as an oxygen-scavenger. In fact, H. Kallfass in U.S. Pat. No. 3,551,349, apparently thought these compounds could not and should not react (see column 2, lines 23-31 of this patent).